1. Field of the Invention
The present invention relates to a solid-state imaging device, a method of driving a solid-state imaging device, and an image processing device.
Priority is claimed on Japanese Patent Application No. 2010-024408, filed Feb. 5, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
Recent imaging devices such as digital cameras, camcorders, and endoscopes include solid-state imaging devices such as charge coupled device (CCD) image sensors or complementary metal oxide semiconductor (CMOS) image sensors. Demands for reduction in size and power consumption of imaging devices are continuously increasing.
There is a solid-state imaging device including a plurality of time analog-to-digital converter type analog/digital (A/D) converters (TADs). A TAD outputs a frequency pulse according to a pixel signal, and a counter counts the pulse, thereby performing A/D conversion on the pixel signal. The pixel signal corresponds to voltage output from a pixel. An area in which pixels are arranged in a two-dimensional matrix is referred to as a pixel block. Japanese Patent Laid-Open No. 2006-287879 discloses a solid-state imaging device having a TAD in which the TAD is disposed in a pixel block to perform A/D conversion on a pixel signal with a high signal-to-noise (S/N) ratio.
A TAD has a nonlinear input/output (I/O) characteristic. Thus, an output value needs to be corrected to make the I/O characteristic linear.
Japanese Unexamined Patent Application, First Publication No. 2004-274157 discloses a method of correcting an output value of a TAD. Correlated double sampling (CDS) is performed on a pixel signal. It is determined whether the resultant voltage belongs to a high voltage region or a low voltage region constituting a voltage region. Using a correction formula corresponding to the corresponding region, an output value of the TAD is corrected.